text:
Where to find out the correct values of AOA of Boeing 737 during different phases of flight?
We can say that practically there are minor differences in AOA for each flight (in the same range of weight). But is there any document that states what flight angle is recommended for each of the flight phases? (takeoff, climb, cruise, descent, and approach)

I don’t believe these differences are “minor.”  A transport-size plane has to operate over a range of weights, and a moving location of CG, that is well beyond anything that can be expressed in a typical POH “table.”  150 KIAS at 90,000 lbs will result in a very different AOA than 150 KIAS at 145,000 lbs.  The dispatcher or the crew will calculate specific Vref’s for various stages of flight, and would be using these speeds, and not AOA, to optimize performance during normal operations.  The crew may know what the limiting AOA is, but would not know or calculate an “optimum” recommended AOA.

You are right Max, there can be major changes in the AOA depending on the weight...I will edit the post

There's no such thing as "recommended angle of attack".
The angle of attack affects the amount of lift generated by the wing. In level flight, the lift of the wing must exactly equal the weight of the plane, so the pilot is just going to fly at whatever AoA gives that amount of lift.
The amount of lift is also affected by the speed at which the airplane flies. So, if the plane speeds up or slows down, the pilot must adjust the AoA to maintain altitude.
There are also things entirely outside the pilot's control that can change the AoA. For instance, updrafts and downdrafts change the direction of the relative wind, which (momentarily) affects AoA.

Normally, in commercial aviation crew operate their aircraft based on speeds and thrust settings. The angle of attack (AOA) that is required for each speed/thrust combination and phase of flight will then be attained by flying the correct speed and thrust setting. As there is no AOA instrument on many (most!) aircraft, this is the normal mode of operation. The speeds which are "recommended" (read: required) for each of these phases of flight are given - or at least roughly explained - in the aircraft manuals, from memory you will have a performance section in the Flight Crew Operating Manual (FCOM) and the Quick Reference Handbook (QRH) for normal and non-normal operations. Some operators elect to publish climb angle data (not: AOA!) for their aircraft in the manuals, and there will be tables for body angle/pitch angle (not: AOA, but at least closer) in the QRH to use as a reference in case the speed indicator fails.
For flying the aircraft, that is all that is required, and the angles are more or less a result of controlling speed and thrust.
If you're really after more detailed data for aerodynamics and flight physics modelling, what you get in the QRH for pitch/power tables may serve as a rough indication for the AOA for various conditions, but it's rounded to whatever crew will be able to read on the instruments and is thus not sufficiently precise for meaningful calculations. More detailed data is only available to aircraft operators and their aircraft performance experts. For example, Boeing used to issue a Performance Engineer's Handbook for their aircraft, which contained more detailed data on aerodynamics and engines. However, these reference books are not publicly available, as from the data you could directly derive information on aircraft performance characteristics which one would rather not share with the competitors.
My favourite book to approximate aero models for real life aircraft, by the way, is Obert's Aerodynamic Design of Transport Aircraft.

I have bought the recommended book, and it is brilliant: simple, and straightforward with crucial information.  Thank you.

Given that is not possible to give proper generic flight angles (it depends on a lot of parameters), I suggest you to have a look to this site. For example you can have a look to the pilot's notes section. Here you can find different notes i.e you can retreive information of the AoA and aerodynamic configurations used in different phases of the flight (e.g here you can find infos about the landing).


text:
Why Ryanair flies from both Stansted and Luton as they are very close
I am doing a research on my future trip from the United Kingdom to the Republic of Ireland and noticed Ryanair flies from both Luton and Stansted to there. Those two airports are quite close to each other - 41 mile by road or 26 miles direct.
In my case, they do multiple daily routes to Dublin from Stansted and multiple daily from Luton as well. The price is similar.
They have a huge base in Stansted and having some unique destinations from Luton (I found at least one - to Bulgaria's Bourgas) means they break the "hub" logic - which is probably not important to them as they don't advertise or support multi-leg routes anyway, but still.
What is the point for Ryanair to fly to same destination from 2 airports located that close to each other? I would understand Stansted and Gatwick as they are on 2 opposite sides of London. Could it be Stansted is getting close to its capability?
On a side note, it must be fun to fly from one to another when a need for this arises! Like a £1000 burger )).

https://commonslibrary.parliament.uk/research-briefings/cbp-9062/ Both Stansted and Luton have limited slots available.  But perhaps the real question is:  Why do people buy tickets from both airports?

When a Ryanair flight is sold out, they cannot substitute a bigger aircraft because they do not have anything outside the range 180-197 seats.  They have to schedule another flight.

So, pretty much, it is the capacity. As for why people buy - I personally consider both when plan to fly anywhere and check the package: parking price, time of flight, return flight time, if I don't drive there I might even fly from one and return to another + consider Gatwick. For me which one does not matter much - to my taste they are quite similar.

With Ryanair that would probably be a £30 burger, unless you wanted to take a bag, in which case it costs about a million pounds.

@GdD - to be fare to them, along with other discount companies they revolutionized air traveling and I personally quite like them - along with Wizz, Jet2, EasyJet and so on. 20 years ago I would not be able to buy a return ticket to Spain for £20 - and I had such trip a couple years ago. Yes, I was only allowed a hand bag, but £20? I spent more just getting to the airport and back!

@GdD As per £1000 burger joke - it is a recreational aviation joke where you fly your Cessna somewhere for fun, have a meal there - a burger :) - and when you are home that burger would be £100-£200. But yours is good as well!

I'm familiar with the $100 hamburger saying @Mykola, I've bought many of them. Or, more accurately a £200 bacon sandwitch and cuppa.

Btw it’s not just Luton-Stansted. Ryanair operate out of Manchester and Liverpool (21nm apart directly, both airports are bases). How about other close bases? E.g. Birmingham and East Midlands, Edinburgh-Glasgow (not a base)-Prestwick?

yes, this would also be of interest. It's just I did not intend to fly from there - hence had not noticed it.

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text:
What are those white things on the windshields of most Citation jets?

What are those white things on the windshield of most citation jets? Does it have to do with rain?

Those are ducts that form the ice and rain protection system for the windshield. That is a vague answer because the precise answer depends on which particular type you look at. The main thing you see is the shroud for ducting air for either anti-ice or rain removal.
Depending on the specific aircraft type, the ice and rain protection systems for the windshield may include one or more of:

Hot engine bleed air for windshield Anti-Icing and rain removal
Application system for alcohol De-Icing (left hand pilot side only)
Movable doors for rain removal
Pressurized (non heated) forced air rain removal system

The first three systems listed above are found on most if not all CE-500 (500/550/560) and CE-525 (M2, CJ, CJ1, CJ2, CJ3) variants (except the CJ4). The last item listed above is found on the CE-560XL type. Other types may also feature one of these systems, but I cannot speak to that with any authority.
The model in your picture is a Citation CE525 M2. I am not familiar with the M2 variant, but I believe it is representative of most CE525 (CitationJet) models up through the CJ3, but not including the CJ4. The CJ4 has an electrically heated windshield with rain repellent applied to the glass and does not have any of the above listed systems.
The main component visible in your photo above is is the shroud that ducts the the engine bleed air to the windscreen. This air is cooled and temperature controlled so as to be at a safe temperature to be applied to the laminated plastic windscreen in flight conditions. This is hot enough that extended ground use could soften or even melt a hole in the windscreen.
My training materials include the following system description which is applicable to most variants of the CE-500 and CE-525 types:

Windshield anti-ice is primarily accomplished by using bleed air to warm both front windscreen exteriors. The air comes out of nozzles within a shroud at the base of each windscreen. A backup alcohol system is provided for the left side if needed.

The Citation Excel CE-560XL type has a visually similar system. However, this system only provides low pressure air for rain removal. This air is ducted from the nose avionics compartment and pressurized by a fan. This air is not heated by the engines. If the avionics compartment builds up excessive heat (such as in extended ground operations) this same system is used to exhaust air from the avionics compartment for cooling.

@J Walters, do you know how the rain doors work?

@Boeing787 They don't work, from what I hear. :) The manual says by creating local turbulence that diverts the rain away from or over top of the windscreen. In over two thousand hours of flying these types I have never used the rain doors, not have I heard from anyone that has. The conventional wisdom is that using them causes them to develop a rattle. Rain removal is not required except in the heaviest rain, and the bleed air system works fine for that purpose.

If you have a look here you will note that they are the outlets for the pneumatic rain-protection-system.
As always, the FAA manual is great to look at if you want more information. Here you can see the kind of system used on a large transport category aircraft [1].

[1] FAA. (2018). Aviation Maintenance Technician Handbook—Airframe Volume 2 (Chapter 15). Federal Aviation Admenstration.

That picture doesn't add much to the answer about the Citation jet. Why not quote some relevant material from the linked document instead of making all of us download it?

This begs the question, what's a "pneumatic rain-protection-system"? Does that replace windshield wipers?

@FreeMan, Aren't windshield wipers lighter than having a whole system for rain protection?

I have no idea, @Boeing787. I'm presuming that a "pneumatic rain-protection-system" is a fancy version of a windshield wiper, but based on this answer, I can't tell, and the one who posted it hasn't come back to share more.

Yes, FreeMan, these rain removal systems replace windshield wipers, which would be lighter. However the rain removal is only a small part of the functions provided.

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text:
What is the raised triangle on the left side of the Garmin G1000?

Looking at one of the official Pilot's Guides shows what looks like could be indicator LEDs inside it, but it doesn't appear to be referenced.... Not that I could find.

Link to Cessna Nav III Pilot's Guide

If you have the plane can you point your phone camera at it and see if you can see purple lights? Then it maybe some sort of proximity sensor

IrDA Port
The maintanence manual explains that in the display diagnostics page, one of the items is

IRDA―Indicates status of GDU 104X IrDA infrared port. Used for Garmin testing, it is not activated at this time

That would be the only thing that looks like an IR port on the display, and its non-use is why it's not mentioned anywhere.
It was envisioned a PDA would be used to exchange flight plans and other data through the port. The G1000 brochure dated 2003 states

The Garmin GDU 1040/1045 is the standard
control/display platform for the G1000’s primary
flight display (PFD) and multi-function display
(MFD)... It’s also
equipped with an infrared port to accommodate
data entry via handheld Garmin PDAs.

I received a response from Garmin Aviation Support:
"Thank you for contacting Garmin International. I believe this is a marker beacon that contains indicator lights for outer, middle, and inner lights.
Best Regards,
[name redacted]
Garmin Aviation Support"
I cannot find anything to corroborate this statement in your manual or elsewhere online. If anyone using a G1000 wants to check this out while flying it could help close this case.

Yes, I saw those, and I know those are not this triangle. I thought perhaps the little triangle can also flash different colors for a marker beacon. But more likely the rep who replied either didn't understand my question or doesn't know.

@codenoob yeah they definitely did not understand.

Okey doke, well I tried. Maybe someone else can shoot support a message and see if they get a more knowledgeable rep (aviation.support@garmin.com)


text:
Which ICAO body designs PANS?
Most air law training documents go at length about how SARPs (Standards and Recommended Practices) are published but nothing about the process related to PANS (Procedures for Air Navigation Services) publications. Is it the same as SARPs? Is it ANC (Air Navigation Commission) technical commissioners developing PANS, submitting them to the council for approbation like for the SARPs?

Is it ANC (Air Navigation Commission) technical commissioners developing PANS, submitting them to the council for approbation like for the SARPs?

1. Similar process for SARPS and PANS
The amendment process for SARPS and PANS is similar, though PANS and SUPPS have not the same status than SARPS. They are SARPS detailed complements.
PANS are designed by technical panels, like SARPS:

How to Build an ICAO SARP, source ICAO
2. PANS approval delegation to the ANC
For PANs, the document is communicated to Council representatives for comments. After comments have be reviewed, and the document has been possibly updated, the president of the ANC approves it.
From Air Navigation Commission - Procedures and Practices:

4.6 Approval of PANS material

4.6.1 In accordance with the decisions taken during the 8th and 12th meetings of the 156th Session (156/8 & 12, C-WP11091), the Council delegated the approval of amendments to PANS documentation (and SUPPS – see 4.7) to the ANC, subject to approval by the President of the Council after their circulation to Representatives on the Council for comment.

4.6.2 Any comments on the amendment proposal received from Council Representatives are discussed with the President of the ANC to determine whether they should be taken into account in the corresponding amendment.

The approved document is submitted with the remaining comments to the president of the Council. If comments asked for a discussion in Council session, the session is held, else the president of the Council can directly approve the release on behalf of the Council:

(4.6.2 cont'd) If  no request is made by a Council Representative to have the PANS amendment tabled for discussion in the Council, the President of the Council will approve the amendment on behalf of the Council and inform the Council accordingly.

SARPS are elaborated in ICAO Annexes. The ANC appoints Technical Panels for both SARPS as well as PANS, there are 6 PANS to supplement and complement the 17 Annexes that the ANC works on.
These two extracts from ICAO PANS documents make things quite clear:

(PANS) contain operational practices that are beyond the scope of
Standards and Recommended Practices (SARPs) but with respect to which
a measure of international uniformity is desir

Procedures for Air Navigation Services (PANS) do not have the same
status as SARPs. While the latter are adopted by the Council in
pursuance of Article 37 of the Convention and are subject to the full
procedure of Article 90, PANS are approved by the Council and are
recommended to Contracting States for worldwide application.

Background:
Popularly known as "The Chicago Convention", The CONVENTION ON INTERNATIONAL CIVIL AVIATION signed in 1944 provides:

Article 37: Adoption of international standards and procedures. (SARPS)

Article 57: Duties of Commission (ANC).

Article 90: Adoption and amendment of Annexes
(a) The adoption by the Council of the Annexes described in Article 54, subparagraph (l), shall require the vote of two-thirds of the Council at a meeting called for that purpose and shall then be submitted by the Council to each contracting State.. . . . .


text:
Why are only discrete SSR codes allotted for aircraft identification?
What happens if we assign a non-discrete squawk code (ending on 00) like 0200?
Is there any particular reason for non-discrete squawk codes to be used only for special purposes and not for identification?

If we only assign the non-discrete squawk code to one aircraft, the radar system would not see the situation as any different than if we assigned a discrete squawk code. Of course the idea behind a non-discrete code is that it may be assigned to more than one aircraft at the same time in the same area.
Older technology had a harder time keeping track of multiple aircraft squawking the same code. Newer radar equipment, particularly (as I understand it) because of technology like Mode S, is better about distinguishing targets even if they are squawking the same code; for example we can have multiple VFR 1200 codes flying around and we can manually associate data block information with each target, and the system will keep the tracks separate. But there is increased risk of confusion (datablock switching or jumping) if non-discrete targets get close to each other, compared to if the targets were on different codes.


text:
What systems are available for landing on aircraft carrier?
Is the old and manual system of "Optical Landing System" (the "meatball") and the Landing Signal Officer(s) the only system for landing on aircraft carriers?

Since you're asking whether the manual system is the only one:
Operational on the F/A-18 is the "AN/APN-245 Automatic Carrier Landing System".

https://www.sncorp.com/capabilities/automatic-carrier-landing-system-acls-radar-beacon/

Also worth mentioning alongside this (ACLS) is ICLS, the instrument carrier landing system, which provides ILS-like glideslope and localizer-style guidance via HUD visual cues. In many implementations, that involves flying the needles manually, but in some conditions it's more reliable than the OLS since it doesn't require visual line of sight.

@Jules, reliability and line of sight are completely unrelated.  You still need to transition to the OLS to land off an ICLS instrument approach. (See my answer to the question I linked in comments above.)

@MichaelHall I meant, reliable in the sense of being available and usable in situations where the IFLOLS system from OCS is unusable because of inclement weather, as well as further out in the approach and landing pattern for a carrier. I don't disagree with the rest of your point.

@Jules ok, the wording of your comment came across as if you thought they were interchangeable and parallel vs complementary and serial.


text:
Do jet nozzles reset after the engine is off for a while?
I have seen jet engines with nozzles being able to dilate to adjust for throttle and things of the sort, but the question I have is, if the engine is turned off, does the nozzle "reset" to a resting or neutral position? Or does it just stay how it was when the engine is switched off. Also, can the nozzles be moved by hand? And does the nozzles' dilation change if the aircraft is left idle for long periods of time?
Specific engines that I would like to know about are the F100-PW-100/200/220/229.

I work with the F100-PW-200/220, so specifically for these engines, i can give you an answer.
The convergent nozzle actuators are mounted to the exhaust nozzle support and consist of one primary and four secondary ballscrew, linear-type actuators.
This answers your first two questions. Since it's not directly hydraulic, the ballscrew actuators will stay in their last position if you just directly shut the engine down.
You can't actuate the nozzle by hand, unless you can somehow rotate the ballscrew actuators.
Edit: To elaborate on this, the nozzle won't return to a neutral position due to the engine switching off and losing hydraulic pressure. The Electonic Engine Control will however - as part of the shutdown procedure - leave the nozzle in a ready position
And for the last question about dilation in idle, the previous answer is correct!
Depends on the pressure in the exhaust section. You don't want to accidentally choke your engine and risk a flame-out.
I don't see the engine ever building up enough pressure to reach this point in idle mode though.

Baring failure, the engine should be in idle before shut down anyway so the nozzle should end up in the same position every time, shouldn't it?

@JanHudec The primary nozzle actuator is driven by two drive cables from the convergent exhaust nozzle control (CENC). The two cables are used to provide a fail-safe mechanism in case one cable malfunctions. The CENC is controlled by the Electronic Engine Control. With the EEC off or inoperative, the nozzle is nearly closed at throttle settings above midrange. The nozzle can be put in a mode, where the nozzle is not scheduled by the CENC but is aerodynamically loaded toward the closed position.

So yep, during normal shutdown with no failure it will always end up in the same position

However with EEC off or inoperative, it would land and shut down with the nozzle towards the closed position.

I see what you mean now @JanHudec although the nozzle won't go to to a "neutral" position when shutting the engine off - the entire shutdown procedure has the engine go to 75-78% power, and then to idle. In which the Electronic Engine Control will adjust the nozzle automatically depending on the pressure in the exhaust section. This automatic adjustment is typically the same every time.

Note that the ball screw actuators for the F100-PW-200/220(E) are driven through the cables by bleed air, not hydraulic power. The edit is not correct when hydraulics are referred to be used for the nozzle opening, furthermore the use of "edit" is not necessary, make it part of your answer instead.

@0scar The edit part is my reddit brain wanting to point out what's new. And though true that the bleed air is what controls the rods, I mention hydraulic power, because that's what most people will think of when talking about moving parts on fighter jets. Note that i mention hydraulic power does not influence the movement of the nozzle.

@Noddle Ah, the shutdown procedure is more complex than I expected.

The reason jet nozzles change diameter is due to efficiency. A jet (or rocket) nozzle is most efficient if the pressure of the exiting gas is equal to ambient air pressure. If the pressures aren't equal, then some thrust will be wasted. This is why rockets have large bell nozzles, to allow the high pressure exhaust gasses to expand and thus lose pressure until it matches outside air pressure as closely as possible.
Variable-geometry nozzles are most often found on afterburning engines. Using the afterburner results in an increase in exhaust gas pressure, so the nozzle needs to expand in order to allow the pressure to drop to match ambient.
Unfortunately, the answers to a lot of your questions are going to be different from engine to engine. I'm not familiar with the specific one you asked about, and a quick Google search didn't turn up anything useful. Nevertheless, I'll answer what I know.

If the engine is turned off, does the nozzle "reset" to a resting or neutral position? Or does it just stay how it was when the engine is switched off?

Since there is no point in moving the nozzle when the engine is not producing thrust, I strongly doubt that there will be any kind of resting or reset position for a given engine. That having been said, if the mechanism isn't perfectly balanced, then residual hydraulic pressure (or just gravity) may push the nozzle into either the fully open or fully closed position over time.

Can the nozzles be moved by hand?

Most such nozzles are hydraulically operated, so whether or not you can move them by hand depends on whether or not the hydraulics are pressurized. Some may be moved by an electric motor turning a jackscrew, and since reverse-driving a jackscrew is nearly impossible, the answer would be "no" in that case.

Does the nozzles' dilation change if the aircraft is left idle for long periods of time?

The diameter of the nozzle depends on the difference between the exit gas pressure of the engine (which may be measured directly or estimated from the engine's current power setting) and ambient air pressure. If neither of these are changing, then there is no reason to change the nozzle.


text:
What does a "runway hold position sign" denote?
I'm wondering why I got this question wrong, as I thought the point of hold positions were to protect aircraft from each other. Any ideas?

Take small comfort that your answer isn’t technically “wrong”, it just isn’t the best answer.

This is the evil of multiple guess questions.  They are diabolically structured with a correct and correctish-sounding answer and are based on the idea that parsing the difference is easy if you know the material really well, and if not, your answer is more of a guess with a 50/50 chance of failure.  Unfortunately, this requires a somewhat lawyerly skill at  linguistic interpretation.  Multiple guess exams must be hell for ESL types.

Welcome to Aviation.SE! The downfall of these multiple choice questions is that they sometimes have more than one answer... You'd think it would be easier with only three options.

You are correct that the general idea of a "runway hold position" sign is to keep aircraft from hitting each other, but that applies to all three answers. You need to tighten your focus a little.
The Aeronautical Information Manual paragraph 2–3–8 is a reference you can use for this question. You can see that a runway hold position sign (2–3–8b1) denotes a holding position short of a runway itself while a runway approach area holding position sign (2–3–8b2) protects the approach (or departure) path to a runway even though the taxiway does not intersect with the actual runway pavement. Your selected answer "C" refers to a runway approach area holding position sign.
That said, I would call the question misleading because both answers "A" and "B" might refer to a runway holding position sign. But if you carefully parse the wording, answer "A" refers to intersecting runways in general while "B" refers specifically to the point where a taxiway enters a runway; a runway holding position sign encountered on another runway does not denote intersecting runways in general but—just like on a taxiway—the point where a runway enters another runway. It's a very fine point, but if I give the test-writer the benefit of the doubt I can see the difference.
...I'll still call it a misleading question though. But it's the sort of question you have to expect from the FAA.


text:
Is my understanding about Balanced Field correct?
We have two definitions:

Balanced Field where Takeoff Distance Required = Accelerated Stop Distance Required

Balanced V1 = This is the speed where on a balanced field length (TODR=ASDR) if we have an engine failure slightly below V1 (Specifically at Vef) we will cover the same amount of distance if we decide to go and reach the screen height of 35 ft or to stop the aircraft at the end of the runway.

Is that correct?

Related: Is "balanced field" defined with or without an engine failure?

Related: What happens if an engine fails between V1 and V2?

You are correct. Never heard the term "Balanced V1" though, but the concept is correct. There is a single V1 where ASDR and TODR are of equal length.

In my understanding, Balanced V1 gives you TODR=TODA in case of take off with OEI (so also after Engine Failure above V1), but In case of EF below V1, ASDR = ASDA

Balanced field concept is not a property of the physical runway, so ASDA and TODA are irrelevant (as long as they are long enough, of course). So you can have balanced field takeoff even if the TODA is longer than TODR or ASDR. But conceptually, any stopway or clearway is irrelevant for balanced field because by definition TOD=ASD, so the shorter one of those dictatates the usable runway length.


text:
Does high speed airflow remove water from the plane's windshield more effectively?
I have read something from the web that mentions higher speed reduces visibility during rain because water spreads over a larger area and the plane impacts droplets more frequently.
I think that statement isn't true because from my point of view the high speed airflow removes water from the plane's windshield more effectively but I am not sure.

Don't believe everything you read on the web, this place is a good example!  I agree with you though...  (got a link to where you read this?)

In all but heavy rain, my car's steeply raked windshield lets me turn off the windshield wipers above 60 mph.

What generally happens is the faster you are going, the rain hitting the windshield disperses into smaller and smaller droplet beads running up the glass and actually becomes less noticeable. There is still a refraction error caused by the presence of droplets, which makes horizontal features like terrain or the horizon look lower than they really are, and you have to be aware of that.
As you slow down, the droplet beads running up the windshield get a bit larger and start to impede vision, especially at night if the rain is moderate to heavy. Under 150 kt, typically on approach, moderate to heavy rain can start to affect the view of the runway ahead and you'll need to turn the wipers on (although I found the wipers to be a bit distracting and didn't turn them on unless I really had to).
Operators will sometimes apply RAIN-X to windshields, especially if the outer lamination is acrylic instead of glass, to minimize the need to use the wipers, which can wear on the softer surface of an acrylic windshield.  RAIN-X is a type of wax like treatment that makes water bead into very fine beads, even at very low speeds.
It can just about eliminate the need to use wipers unless rain is extremely heavy.

I love my RAIN-X!  Are we allowed to promote products here?

Prolly not lol.  My beef with it, when used on a car, is the wiper leaves behind micro beads created by the coating, and it looks like a smear. So if it's applied, you have avoid the wipers except in extreme cases.


text:
Does making a mistake mean you lose your cert?
Disclaimer: I haven't been in, nor do I plan on having an accident. That said, this has always been a question of mine.
Let's say I'm flying a little Cessna or ultralight around Ohio. Maybe the wind is stronger than expected aloft and I run out of gas before making it back home. Clearly I need to put it down on a road or field if I can.
After this happens, does the FAA revoke your certificate?

Closely related

If you're a US Senator, you can land on a closed runway, "sky hop" over the construction workers on that runway, and land again and not lose your certificate.

I have read that if you run out of fuel you can forget ever getting insurance. Don't know how accurate that is.

"Clearly I need to put it down on a road or field if I can." To keep this hypothetical scenario from becoming reality, you can keep track of your radius of range. Yes, I like that concept. Basically, always know for how much longer you can stay in the air; know what this means in terms of distance with current winds (unless it's absolutely calm, your "radius of range" will form an ellipse, and you won't be at the center of it); and know which possible landing airports are available within it. Any port in a storm.

Probably not.  Depending on how poor your planning was (or appeared to be) you may have nothing happen, have letter placed in your file (not a violation), receive a violation, have to make a 709 ride with a Fed, or have your cert suspended, or maybe even a combination of some of these.
If you were a real goober and just went flying without checking fuel, and then lied about checking fuel, and then get caught lying to federal investigators then, yeah, revocation is a realistic possibility.  They don't like liars.  They can deal with stupid mistakes, but they will not tolerate a liar.
//thanks for the edit but was written as a runon//

There are very few instances of revocation, typically suspension with retraining is assigned to the offending pilot. Even when two airline pilots missed their airport by 110 miles and ignored ATC for 90 minutes had their licenses "revoked" but could reapply for them after just 10 months and taking all required tests/training for the licenses again.

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text:
Is the shape of the Bell X-1 wing on Virgin Galactic's VSS Unity's artwork correct?
This answer to the Space SE question What do these patterns on Virgin Galactic's VSS Unity represent, and how are they applied? indicates that one of the aerospacecraft representations on the Unity is the Bell X-1, and comments there suggest that the shape of the wing might not be completely accurate.
It may be possible that the shape evolved during development, but I'd like to ask;
What is the shape of the Bell X-1 wing, and is the representation of it in the artwork on Virgin Galactic's VSS Unity correct?

above: Screen shot from the Virgin Galactic YouTube video VSS Unity | Third Rocket Powered Flight.

above: from this answer and Virgin Galactic.

Even the image of the Wright Flyer isn't all that great, it had 2 "rudders" and not so many support sticks going back to it.

It also looks like the 747 is blasting the LEM with 4 x 50 cals in the top picture.

Also, the  Ryan NYP (Spirit of Saint Louis) is shown with much too short a wingspan compared to overall fuselage length.

According to this NACA (now NASA) Technical Report [Wing Loads on the Bell X-1 Research Airplane (10 Percent Thick Wing) as Determined by Pressure-distribution Measurements in Flight at Subsonic and Transonic Speeds], the wings look a bit different to the one used by Virgin.

But there might be different versions of the wing, since there were multiple versions of the X-1.
The wikipedia article shows yet another wing geometry.

Below is a composition of 3 different drawings I found via google, which show that at least there exist various different drawings of the wing

The most obvious difference is that the Virgin artwork version has a straight trailing edge and a more highly swept leading edge than the real thing. This should be included in the answer.  Why do you say the Wikipedia version resembles the Virgin artwork version?  Just because of the wingtip probe thingies?

the answer does not state that the wikipedia article shows the version used by Virgin. I tried to show that there seem to be different versions of the wing.

That's better now!

This particular wing shape on the Virgin Galactic artwork is definitely wrong.
Given the historical context, the top-down view graphic of the Bell X-1 is used to depict the version which famously broke the sound barrier on October 14, 1947. with Capt. Chuck Yeager at the controls.
This was the USAF aircraft #46-062 (nicknamed Glamorous Glennis, after Chuck Yeager's wife), and the flight number was XS-1 #50.
It is now on permanent display at the Smithsonian Air and Space Museum.
References:

https://en.wikipedia.org/wiki/Bell_X-1
https://en.wikipedia.org/wiki/List_of_X-1_flights
https://airandspace.si.edu/collection-objects/bell-x-1

Could you explain how exactly the artwork is wrong? What is different from the real X-1 shape?

@Bianfable the most obvious difference is that the Virgin artwork version has a straight trailing edge and a more highly swept leading edge. This should be included in the answer.


text:
How unusual is it for remotely piloted aircraft to fly through commercial or general aviation airspace?
According to the Phys.org article NASA flies large unmanned aircraft in public airspace without chase plane for first time:

Flights of large craft like Ikhana, have traditionally required a safety chase aircraft to follow the unmanned aircraft as it travels through the same airspace used by commercial aircraft. The Ikhana flew in accordance with the Federal Aviation Administration's (FAA) Technical Standard Order 211—Detect and Avoid Systems—and Technical Standard Order 212—Air-to-Air Radar for Traffic Surveillance.
[...] The Ikhana aircraft was equipped with detect and avoid technologies, including an airborne radar developed by General Atomics Aeronautical Systems, Inc., a Honeywell Traffic Alert and Collision Avoidance System, a Detect and Avoid Fusion Tracker, and an Automatic Dependent Surveillance-Broadcast capability – a surveillance technology where the aircraft determines its position via satellite navigation and periodically broadcasts this information so other aircraft can track it.
The flight took off from Edwards Air Force Base in California and entered controlled air space almost immediately. Ikhana flew into the Class-A airspace, where commercial airliners fly, just west of Edwards at an altitude of about 20,000 feet. The aircraft then turned north toward Fresno, requiring air traffic control to be transferred from the Los Angeles Air Route Traffic Control Center to the Oakland Air Route Traffic Control Center. On the return trip, the pilot headed south toward Victorville, California, requiring communication control to be transferred back to Los Angeles.
During the return flight, the pilot began a gentle descent over the city of Tehachapi, California, into Class E airspace—about 10,000 feet—where general aviation pilots fly. The pilot initiated an approach into Victorville airport at 5,000 feet, coordinating in real time with air traffic controllers at the airport. After successfully executing all of these milestones, the aircraft exited the public airspace and returned to its base at Armstrong.
"We are flying with a suite of sophisticated technology that greatly enhances the safety capabilities of pilots flying large unmanned aircraft in the National Airspace System," said Scott Howe, Armstrong test pilot. "We took the time to mitigate the risks and to ensure that we, as a program, were prepared for this flight."
Tuesday's flight was the first remotely-piloted aircraft to use airborne detect and avoid technology to meet the intent of the FAA's "see and avoid" rules, with all test objectives successfully accomplished.

At the end of the article:

More information: For more information on NASA's Unmanned Aircraft Systems Integration in the National Airspace System project, visit go.nasa.gov/2sx9VCn.

Question: While this was the "...first remotely-piloted aircraft to use airborne detect and avoid technology to meet the intent of the FAA's 'see and avoid' rules, with all test objectives successfully accomplished", (without a chase plane?) how rare is it for remotely-piloted aircraft to fly through US airspace where commercial or general aviation also flies without all those extra qualifications? Has this happened several times, several hundred, daily? Is it even more infrequent without a chase plane?

Click images for full size.
above left: "Aircraft maintenance crews at NASA‘s Armstrong Flight Research Center prepare the remotely-piloted Ikhana aircraft for a test flight June 12, 2018. The test flight was performed to validate key technologies and operations necessary for the Federal Aviation Administration's approval to fly the aircraft in the public airspace without a safety chase aircraft." Credit: NASA/Ken Ulbrich
right: "NASA’s remotely-piloted Ikhana aircraft, based at the agency’s Armstrong Flight Research Center, is flown in preparation for its first mission in public airspace without a safety chase aircraft." Credit: NASA/Carla Thomas

The military has been doing it for decades - they just don't tell anyone.

note: edit was me, I forgot to log in so it shows as anonymous user.

In the US, the main operators of large UAS (i.e. non CFR Part 107 aircraft) are Air National Guard (MQ-9) and the Department of Homeland Security (Customs and Boarder Protection, also MQ-9). Here is a table from the Pentagon on how many missions UAS flew domestically in FY2018. (Note that these are "missions" and do not include other types of operations such as training or flight test, see below.)

A report from OIG published in 2014 lists a total of 5,102 flight hours by CBP in FY2013 (which is supposed to be closer to 26,000+, hence the OIGs investigation). Air National Guard also operates MQ-9 domestically for frequent training missions and contractors such as General Atomics Aeronautical Systems, Inc. and Northrop Grumman operate a fleet of capital aircraft at their respective training centers (e.g. Grand Forks). Lastly, of course, NASA also flies UAS. An example of how such missions are executed is described in this NASA report on the Western States Fire Missions starting on page 30.
So on your question about frequency: Assuming that the sum of all those aircraft result in ~5x number of flight hours, you'd be looking at something like 25,000 yearly flight hours in the US National Airspace System of large Remotely piloted aircraft. This is likely on the low side given the OIGs observation about the operational tempo of the CBP fleet.
So Why Is This Demonstration Relevant?
You may ask: if we're already operating these aircraft without chase planes, what was so special about this flight? It was the ability to fly a UAS without a chase plane without first having to climb to Class A airspace.
FAA Notice 8900.227 stipulates the requirements for how to obtain operational approval for an unmanned aircraft; specifically, it states:

... compliance with the see-and-avoid requirement [is a] primary concerns in UAS operational approvals leading to [...] the use of observers [to maintain] flight separation and collision avoidance or ‘segregation’;

In the case of a flight with a chase aircraft, that visual observer is onboard the chase aircraft. This is also where the "Visual Line of Sight Requirement" comes from - the observer/pilot must be able to see the aircraft during the operation.
There is one exception in N8900.227 for the visual observer (VO) requirement:

VOs are not required in Class A airspace [...]

As a result, so far operations of the above-mentioned agencies occur almost exclusively in Class A airspace; i.e. above 18,000ft. Since those entities are either government agencies or contracting with a government agency, access to restricted airspace is straight forward where these aircraft can circle up or down to and from Class A airspace. In the case CBP and Global Hawk operations in Grand Forks there is a Temporary Flight Restriction that enables this access to Class A airspace without the need of a chase aircraft below 18,000ft.
This type of operation is incredibly inefficient though (imagine if manned aviation had to operate like that). As a result, and that is what makes this NASA flight unique, the ability to use an onboard system to detect and avoid other aircraft (i.e. a Detect and Avoid System) when operating in airspace other than Class A, in particular Class E below 10,000ft where "non-cooperative" aircraft operate removes a list of operational limitations. From N8900.227 again:

b. Risk Mitigation. While considerable work is ongoing to develop a certifiable detect, sense, and avoid system as an AMOC with the see-and-avoid aspect of §§ 91.113 and 91.115, no current solution exists.

The "considerable work" mentioned refers to this NASA project - and the flight was the capstone demonstration to show equipment in fact can serve as an Alternate Means of Compliance (AMOC) when operating outside of Class A airspace.

Thank you very much for such a thorough answer, and for identifying the more significant and underlying question So Why Is This Demonstration Relevant? (or newsworthy)

To answer the latter part of your question according to FAA regulations no UAS' may fly out of line of sight or without a chase plane:

Flights below FL180 must have a dedicated observer. These duties may
  be performed by a ground based observer or chase plane.

So in according to the legislation it never happens, at least not regularly. You can get a waiver from the FAA to bypass this as is outlined in this question.
Its hard to say how often this happens with chase planes as there is nothing against the regulations on it and there may not be much in the way of reporting when it happens. This podcast discusses some of the sub scale testing NASA does and according to the engineer being interviewed they are only flying a test airframe once every few months. You can find a nice listing of the various tests and things that NASA is up to here.
Most notably NASA has been using some old globe hawk drones to monitor hurricanes off the cost of Florida. It does not seem this is a regular occurrence and its unclear in what airspaces it flew.
The answer boils down to not all that often.

That darn NASA; next thing you know they'll be trying to putting things in outer space without pilots!


text:
Is falling a mode of flying?
I frequently observe people arguing (on this very web site) about the question if falling is a mode of flying or not. It appears to me that the majority of people have a strong opinion that it is not.
Surely it is a matter of definition. I made the effort to look it up in a number of online dictionaries. Most sources provide many possible options to define flight, like Merriam-Webster:

1a : an act or instance of passing through the air by the use of
  wings

but it continues with

2a : a passing through the air or through space outside the earth's
  atmosphere

Wikipedia tried to put everything into one paragraph:

 Flight is the process by which an object moves through an atmosphere (or beyond it, as in the case of spaceflight) without contact with the surface. This can be achieved by generating aerodynamic lift associated with propulsive thrust, aerostatically using buoyancy, or by ballistic movement.

Flight may be aerodynamic, propulsive, aerostatic, or ballistic.
When one throws a ball, the ball is flying. It flies until it hits anything else than air. Why would it be different if the ball is thrown upwards, or pushed downwards, or just dropped?
In my understanding, falling is just a very special case of flying. Is this correct?

By this definition, so is hovering?

@user3528438 I would say so. It would be strange if a helicopter stopped flying while it is hovering.

Can you link to one of the specific discussions you mentioned on this site? As you said, this comes down to what definitions you use and  I'm not sure what the context is. As written, I don't see a lot of point in defining the terms formally but for all I know it is important for some people.

@Pondlife I'm afraid not. These discussions happen in the comments which are not persistent. The context is the usage in this site, and clarifying terminology should be in everybody's interest.

There's a reason we use the term "sustained flight" to get rid of all the ambiguity.

I don't think this is a good question.  What is the definition of falling?  Downward component to trajectory?  Ballistic trajectory?  Zero motion in horizontally forward direction?  Zero aerodynamic force acting perpendicular to flight path, i.e. zero lift?  Vertical speed component increasing rather than steady-state?  We can't answer without knowing which you mean.  I know we've had some answers that suggest if aircraft is sinking but nose is pointed above horizon then that is in some sense a "fall".  I don't think those were good answers.

Also, is an orbiting spacecraft "falling" according to common sense and also according to your chosen definition of "falling" from the list above?  It's not so simple to define "falling" is it.  Is the earth "falling"?

Falling is half the equation.  If you weren't falling, there'd be no need for the wings.

But, it is understandable that answers that include interpretation of concepts may be not perfectly suitable to the rules of this site, but sure can make for some great discussion!

Reminds me of Harold, the flying sheep. Well, he doesn't fly so much as plummet.  http://www.montypython.net/scripts/flysheep.php

No, falling is not flying.
Sources:

The land before time (1988): Falling is easy, flying is difficult.
Douglas Adams (1979), The Hitchhiker Guide to the Galaxy
Toy Story (1995), Falling with Style

When I read your answer I thought it was a Douglas Adams reference :-)

I was expecting the video from Toy Story, Falling with Style.

@Pondlife Even better! I made my post into a community wiki and hope that everybody will add their favourite "falling vs flying" reference from popular culture.

I pleases me that this answer has more upvotes than the obtuse rationalizations offered on both sides of the argument. Sometimes we forget common sense definitions. Flying is the exact opposite of falling:  It is the ability to overcome gravity to travel through the air. Webster and others back this up...

Since falling is just the final result of a ballistic arc if you let it go long enough, and ballistic arcs are considered "flight" per the Oxford Dictionary (as in the ballistic arcs of balls, spacecraft, arrows, etc being considered "flights"), then technically, a falling object is in flight.
You could give it just the tiniest lateral push when you drop it so it goes down with a slight ballistic curve;  in the end, no different from driving it laterally so it has horizontal energy/inertia with a high velocity that exactly counteracts gravitational pull, and give it a vacuum so it can do that indefinitely - a satellite - , the only difference being that and the ball being the location in or out of the atmosphere and energy put into it.
In other words, orbital vehicles, baseballs, bullets, are all "falling" and are technically in flight, and so is a ball you drop straight down... if the Oxford Dictionary definition is what you want to use.
In my own airplane, if I push over with just the right elevator input, and go zero G, my plane is now in a ballistic arc.  The wings are superfluous, for a few seconds anyway, and my plane is "falling", just not straight down.  So if you accept that in that condition it is still "flying", the falling is flight.

A fall is the collective sequence of deterministic states describing the instants between an initial condition (any initial condition, i.e. either releasing an object from a height into the air, releasing an upwards-thrown ball, etc.) and a final condition/state, which are predictable in their entirety, based on Physics. If you take everything into account (air composition, density, object mass distribution, center of gravity, gravitational acceleration and its variation with height, air resistance, centrifugal force, Coriolis force, Euler force, everything), then you can calculate the final conditions from the initial conditions with very high fidelity. It doesn't matter that the mechanics are spectacularly complex and the necessary information is huge, in volume. In Physics, you can usually work your way out of complexity by simulating, which still provides an adequate degree of accuracy when adequately modelling the states. The difference lies, therefore, in the inertness of the falling object!
In contrast, when in flight, no amount of intermediate instance state information (even given the initial conditions) can allow an external observer to predict a state that could be rendered as final. In fact, only short-lived predictions can be made for a flying object by anyone not actively influencing the object.
In short, when you see something falling, you always know what happens next (or soon after). Ball lands, projectile drops, plane crashes, etc. According to this, a flying squirrel flies because you cannot predict the landing point at any point after its jump and while airborne. Only the animal knows what it's trying to achieve and it's actively exploiting Physics to make it happen (after much training, of course!).
So, falling is flying only... in the face of science!

The final state of a glide (flight) can be predicted by holding conditions constant, simply ask the squirrel to do its best to hold them throughout its flight.

Well, this is "bending the rules" a bit. But technically, holding conditions constant is not flight, it is falling... with style!

What is the definition of falling? Downward component to trajectory? Ballistic trajectory? Zero motion in horizontally forward direction? Zero aerodynamic force acting perpendicular to flight path, i.e. zero lift?  Vertical speed component negative and increasing rather than steady-state?  A non-zero acceleration component acting perpendicular to the flight path and also acting at least partially earthward, not skyward?  (I.e. semi-ballistic trajectory due to insufficient lift.)  Or something else?  We can't answer without knowing which we mean. Some have suggested that if an aircraft is sinking at a constant rate but the nose is pointed above the horizon, then that is in some sense a "fall". Many would not agree.
Is an orbiting spacecraft "falling", according to common sense?  And how about according to your chosen definition of "falling" from the list above?  It's not so simple to define "falling", is it.  Is the earth "falling"?  Is the earth "flying"?
Implicit in this answer, is a hint that the question may not be a very useful one, because it is insufficiently constrained.  But this may shed some light on possible answers nonetheless.

You don't need my definition of falling to answer this question, because I mean any of them. From the ones you have listed, is there one that is not a particular case of flying?


text:
Are there any preventive measures against bird strikes while in flight?
Most of the preventive measures for bird strikes are at/around the airport but what are some of the ways that can be used to prevent bird strikes on the plane as it is climbing or in flight?

With the notable exception of US1549, bird strikes just aren't serious enough to actively avoid.  The risk to the passengers and flight crew of aggressive sudden movements is much higher than the risk of just hitting the bird.

There's more than one time an airplane has been brought down by birdstrikes, I wouldn't be so dismissive @abelenky. Ryanair 4102 comes to mind, and there are more.

In FR4102, 10 people received minor injuries, after multiple bird strikes on short-final.   I think that proves the point:  Hitting the birds is safer than any known avoidance techniques.

Airports engage in a number of strategies to reduce the number of birds nearby that might cause strikes. This has been addressed in a previous question: What are the ways to keep the birds away from airfields?
Avian Radar also exists:

Avian radar[44] is an important tool for aiding in bird strike mitigation as part of overall safety management systems at civilian and military airfields. Properly designed and equipped avian radars can track thousands of birds simultaneously in real-time, night and day, through 360° of coverage, out to ranges of 10 km and beyond for flocks, updating every target's position (longitude, latitude, altitude), speed, heading, and size every 2–3 seconds. Data from these systems can be used to generate information products ranging from real-time threat alerts to historical analyses of bird activity patterns in both time and space.

https://en.wikipedia.org/wiki/Bird_strike#Flight_path

Installations include civil applications at New York/John F Kennedy International Airport, Chicago/O'Hare International Airport and Seattle-Tacoma although the majority of both deployment and development activity is still focussed (sic) on military air movements.

https://www.skybrary.aero/index.php/Detection_of_Bird_Activity_Using_Radar

MERLIN Avian Radar System technology...is used...to detect and monitor hazardous bird activity on and around airfields for bird-aircraft strike hazard management.

https://detect-inc.com/bird-control-radar-systems/

i'm not asking about the preventive measures that are on the airport but on the aircraft its self like an instrument of that sort @zymhan. i'm doing a research

@greezyronald updated the post

In my Cessna 172 my eyes are the only advance warning system available.  I've used them a couple of times to avoid large birds, and not necessarily on approach.  I also know of several bird strikes in small planes that are just good stories after the clean up at the airport.  On the other hand, I also have heard of windscreens being shattered but the pilot still being able to maintain control and land the aircraft normally.
I suspect your question was written with airliners in mind, but bird strikes are not uncommon in small airplanes, and the results are mostly unremarkable.

See and avoid. Avoid not always possible, especially when moving fast and you don't see it/them coming, or are just not that maneuverable.

No such thing as see and avoid in jets, except possibly for a huge flock of geese off in the distance, above the horizon (they are invisible below).  A jet on a departure profile has no way to dodge birds, and once you are above 5000 ft, the chance of a bird encounter drops to vanishingly small, to almost (but not quite) zero above 10000.


text:
How will the altimeter read in air colder than ISA?
When flying in air which is colder than ISA (International Standard Altitude), how will the altimeter read compared to true altitude?
My manual says the altimeter will over read - why?

Are we assuming that the density of the air is the same as what ISA specifies? (Or maybe we don't need to assume anything—does the density of atmospheric layers generally stay the same regardless of temperature?)

"In winter the mountains become taller"

Air expands as the temperature increases and it compresses when the temperature decreases.

image source: aviationweather.ws
When it is colder than ISA, the air column is compressed and therefore you are flying lower than the altimeter is indicating. In other words: the altimeter will over read in cold air.
So to fly safely over an obstacle at a cold day, you have to add extra margin to the obstacle's height, because your altimeter will show a higher altitude than your true altitude.

I don't really understand what you're saying here. You're saying that air becomes less dense as the temperature increases and less dense when the temperature decreases. When it is colder than ISA, the air column becomes more dense. But how is that relevant? Altimeters don't measure density, do they?

@TannerSwett Altimeters measure pressure and convert that to an altitude based on the assumption that the pressure distribution is according to ISA. Pressure becomes lower as you get higher, because the weight of the atmosphere above you gets lower as you get higher (i.e. there is less atmosphere above you when you get higher). If the density is higher (e.g. because of cold) the gradient at which the pressure drops is steeper. So the pressure that is normally (in ISA) found at 10 000ft will on a cold day be found at e.g. 9500 ft.

Ah, I understand now. I was thinking of compression locally (in a given patch of air, the molecules get closer together), whereas you were talking about compression on a large scale (in a given column of air extending from the ground up to space, the "pressure layers" get closer together). Right?

@TannerSwett exactly.

I'm studying for my PPL and this concept has always given me fits.  Your picture is the best illustration by far I have seen.

@Koyovis, at constant true altitude, the colder the day, the higher the indicated altitude on the altimeter. So to fly safely over an obstacle at a cold day, you have to add extra margin because your altimeter will show a higher altitude than your true altitude.

DeltaLima has it right, though I still always find it counter-intuitive.  I mean, wouldn't denser air mean your altimeter will read lower?
But--the thing to remember is that it's not the weight of the air above you, it's the weight of the air below you.  The altimeter is calibrated to the pressure reported by the ground station. Therefore, it IS accurate on the ground.  But colder, denser air, as DeltaLima points out, will have a steeper pressure gradient--so as you climb above ground, the altimeter indicates altitude rising faster than the true height.
The moniker is: "High to low, look out below": as temperature falls, you are lower than you think!

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How to calculate the real Ground Speed from True Air Speed?
In most of the formulas I've found online GS = TAS + Vw, i.e. true air speed plus wind.
However, on the simulator, GS changes drastically if I dive or climb which is obvious because I'm covering 0 ground distance if I dive vertically.
What is therefore a real GS formula from TAS? It has to take into account the wind (Vw) but also the "3D angle of the aircraft" (for the lack of better expression).

If you have a non-null GS when flying vertically, then your simulator has a problem. Likely duplicate of Why is there a difference between GPS Speed and Indicator speed?

Not necessarily: With pitch of +/- 90 degrees, you might still have a lift generating AoA, depending of angle of incidence etc. Even considering a zero-lift vertical dive, horizontal wind component could still cause positive GS.

...(this of course depends on how one defines "flying vertically", if you mean "with indicated attitude of +/- 90 degrees", then my comment applies)

@Waked: "Vertically" as the OP described very accurately: "I'm covering 0 ground distance"

@mins and in that case you are correct, by definition. I was allowing for the possibility that the OP incorrectly deduced that "nose pointing straight up/down" automatically results in "covering 0 ground distance".

@mins: Not necessarily.  If you are flying vertically - that is, at a 90 degree angle to the (flat) ground, your ground speed will be whatever the wind happens to be, no?  If you have a GPS, it will indicate this speed.

@jamesqf: Yes, but here vertical is qualifying the trajectory, not the attitude, as the OP says "I'm covering 0 ground distance".

First calculate horizontal component of airspeed, then add the wind:
$$v_{GS} = cos(\theta) * v_{TAS} + v_{wind}$$ with $\theta$ being the angle between the horizon and the path of the aircraft in the vertical plane.
Or, if you are unfamiliar with trigonometry (using Pythagora's theorem):
$$ v_{GS} = \sqrt{v_{TAS}^2-v_{verticalSpeed}^2} + v_{wind}$$
Both formulas assume the same units being used for all speeds ($v_{TAS}$, $v_{verticalSpeed}$, $v_{wind}$), and only take horizontal wind into consideration. $v_{wind}$ is only considering the headwind/tailwind component.

Pitch angle being pure pitch value, regardless of roll and yaw?

Well, more correctly, the angle between the horizon and the actual flight path. This example is in straight flight, ie not turning. If you'd like to involve turning flight (roll/yaw) you'd also have to decide along what you want to calculate ground speed. Along the turn radius or along an arbitrary vector?

Along the turn radius.

Actually, although acceleration is directed towards the center of the turn, at any given moment, the velocity of the aircraft will always be tangential to the turn (given coordinated flight). This means that the formula still applies. If you wanted to, you could parameterize head/tailwind ($v_{wind}$) as a function of time, $t$ to calculate $v_{GS}$ at any given $t$. This would involve finding the rate of turn (function of gravity constant, bank angle and $v_{TAS}$). What is it that you need the formula for?

@Weaked I need it for getting the ground speed to calculate waypoint arrivals for missions. I can read IAS, but rest I have to calc. Now, how to get "angle between the horizon and the path of the aircraft in the vertical plane"? With "rate of turn " as you mentioned?

The ground speed and the wind speed are both vectors, and you cannot just apply a scalar summation to them.

In the context above, I'm considering all terms as scalars (hence my comment about $v_{wind}$ only being the direct head/tailwind component). Speed is, by definition, a scalar. I could possibly have been a bit more careful by using something else than $v$ as a symbol, but this is convention in grade/high-school physics at least where I'm from.

A real GS formula from TAS takes into account two velocity triangles: one with the vertical velocity, and one with the wind velocity.

Vertical velocity. Here's the velocity triangle. With no wind, we get:

$$ cos(\Phi) = \frac {GS}{TAS} \tag{1}$$
 $$ sin(\Phi) = \frac{V_C}{TAS} \tag {2}$$
And we know from math lessons that $sin^2(\Phi)$ + $cos^2(\Phi)$ = 1, so:
$$\frac {GS^2}{TAS^2} + \frac{V_C^2}{TAS^2} = 1 => GS^2 + V_C^2 = TAS^2 => $$
$$GS = \sqrt{TAS^2 - V_C^2} \tag{3}$$.

Wind speed. The equation in the OP just adds wind speed to the TAS, and this is only valid if the wind direction is the same as the flight direction. This is usually not the case, and we will need to consider another velocity triangle, this time from the viewpoint of looking down on the plane:

In this example, $\Phi$ = 70-30 = 40°. The cosine of the wind speed we can add directly to the ground speed, the sine component will need to be added in a Pythagoras way.
$${V_{TOT}}^2 = (V + V_W \cdot cos (\Phi))^2 + (V_W \cdot sin (\Phi))^2$$
=> $$ {V_{TOT}}^2 = V^2 + 2 \cdot V \cdot V_W \cdot cos(\Phi)+ {V_W}^2 \cdot cos^2(\Phi) + {V_W}^2 \cdot sin^2(\Phi)$$
 and again since $sin^2(\Phi)$ + $cos^2(\Phi)$ = 1
 $$ {V_{TOT}}^2 = V^2 + {V_W}^2 + 2 \cdot V \cdot V_W \cdot cos(\Phi) \tag{4}$$

Combine equations (3) and (4)

$$ GS = \sqrt{TAS^2 - {V_C}^2 + {V_W}^2 + 2 \cdot \sqrt{TAS^2 - {V_C}^2}\cdot V_W \cdot cos(\Phi)} \tag{5}$$

Is Vertical velocity coming directly from instruments?

There is an instrument that directly indicates the vertical speed, but it has a time delay. Since vertical speed is measured as altitude compared to altitude some time ago, the time delay is inherent since we're measuring a time derivative.


text:
Are there any standards on the dimensions of PFD symbols?
Are there industry standards on dimensions of PFD symbologies like heading, airspeed and altitude?
I want to design a 15 inch screen and wonder if there are any standards or regulations regarding the design of those information displays.

Welcome to Aviation.SE! Could you please further clarify your question? Are you asking how this is done in general or are you involved in developing a PFD system?

I'm trying to design Primary flight display for a flight simulator. I want to know the height and width of the symbologies generally used for a 15 inch display screen.

Could you fit a 15 inch display in a cockpit? That is quite large.

15 inch diagonally .

Yes, so is my laptop - and it won't fit in the panel of my plane.

15 inches displays are used in planes. For example Boeing 787 has five MFD of 15 inches each.

Yes there are standards. There are industry standards which not regulatory standards, but they have been deemed acceptable by the regulatory agencies (e.g. FAA). So following them is usually accepted without issue.
The FAA also provides guidance in the form of an Advisory Circular, AC 25-11B Electronic Flight Displays.
You have two separate things to address; the actual display hardware and the displayed content.
The standard for the hardware is SAE Aerospace Standard AS8034B, Minimum Performance Standard for Airborne Multipurpose Electronic Displays.
The rest is covered under a group of SAE Aerospace Recommended Practice (ARP) documents. The top level is ARP4102, Flight Deck Panels, Controls, and Displays. Under it are several Volumes and Appendices.
ARP4102-7, Electronic Displays, covers the general requirements for what must be displayed.
ARP4102-7 Appendix A, Electronic Display Symbology for EADI/PFD, covers the details for the PFD. Appendix B covers the EHSI/ND and Appendix C covers the Engine displays.

Aerospace Recommendation Practice does mention the font size. But it doesn't mention the dimensions of symbologies. For example, how do i decide the dimension of airspeed indicator? assuming viewing distance of 30 inches for a 9 X 12 inches screen .

There's a fair amount of flexibility in the display of symbols. The key issue is that they need to be easily discernible, recognizable, and accurately positioned. The size and resolution of the displays and the allowable installed viewing distance will force trade offs in the symbol design. If you look at existing displays, you can find some wide variation in design. AC 25-11 provides the most recent guidance.


text:
What type of mechanism is used to operate the Embraer EMB 120 front door?
I have never worked on this type of aircraft, but I usually come across it in several hangars. I've been wondering on which mechanism this bulk door is lowered and lifted.
Is it by pneumatic system, hydraulic system or by electrical motors?

From the EMB120 Ops Manual:

FORWARD ENTRY DOOR
The forward entry door incorporates a folding air stairs and is fixed
  at the fuselage's lower edge.
The door can be raised manually or hydraulically. For normal
  operation, two hydraulic actuators powered by the green hydraulic
  system or by an accumulator, raise the door. This actuator has the
  capability of performing four complete operations and is controlled
  from the INTERIOR FWD DOOR CONTROL PANEL (ATTENDANT'S PANEL) or from
  EXTERIOR FWD DOOR CONTROL PANEL. Each panel incorporates a pushbutton,
  which energizes a solenoid valve that allows hydraulic power to raise
  the door. A blue light illuminates while the door is moving up. This
  system's circuit breaker is located at the INTERIOR FWD DOOR CONTROL
  PANEL (ATTENDANT'S PANEL).
The door may be raised manually by an outside ground attendant who
  lifts the door to its closed position.
The spring accumulator is located in the hydraulic compartment at the
  right side of the fuselage forward section. Once the door is raised,
  moving the red inner or outer handle down will latch it. The hydraulic
  circuit provides a damping function when the door is opening.
The hydraulic circuit is provided with an emergency valve, which
  allows the forward door to be lowered when the solenoid valve fails.


text:
How close are planes allowed to fly next to each other?
I have a question - how close are planes allowed to fly when their paths are about to cross? I am sure there are proximity warnings and what not but I also know those accidents happen, even if not that often.

I was on board of a KLM flight from Amsterdam to Madrid and sometimes in the later part of the flight, if I recall correctly, another plane, flew just below us. Of course, I imagine human vision, mine included, is probably not the most reliable source. However, I saw the plane and in less than 1 second it speeded right below us, so I imagine that it was quite close. However, I felt no turbolence after it passed.
Given that description, can you let me know your thoughts - how close in reality it was? Of course if it helps, I can give you the flight number and day.

This looks like a dupe of this question, at least if it's about European regulations. However, this question has an answer, the other one doesn't.

@Pondlife I marked the old question as a dupe of this one per numerous answers on meta

Your plane was at least 300 meters above the aircraft you saw.
The limits are determined by the altitude and capabilities of the aircraft.

Up to 29,000 ft - 300 meters vertical separation
29,000 ft and above - 600 meters
29,000 - 41,000 ft (where there is RVSM (Reduced Vertical Spacing Minima)), the minimum separation is 300 meters, but the aircraft have to be equipped with specific instruments. Most modern airliners are equipped to fly in RVSM approved airspace.
41,000 feet - 60,000 ft, 300 meter RVSM
60,000 feet and above, 1.5 KM irrespective of RVSM

You won't feel turbulence unless you are flying behind an airplane, or you fly into an airplane's wake.  Turbulence happens in disturbed air and this is usually behind the airplane's wingtips.
All modern airliners are equipped with TCAS (Traffic Collision Avoidance System); which consist of visual indicators on the relative position of nearby aircraft.
Here is an image from flightgear wiki that shows how this looks on some modern airliners:

Hm, that TCAS example does not make much sense. If the plane is 1300 ft above and climbing, it should not be threatening, since that would require you to be climbing by about 2000 ft/min faster and that's extremely unlikely.

I believe it is just for illustrative purposes and not an actual screen capture.

No closer than 500 feet above or below, and more likely 1000 feet if both were commercial flights. Side by side, they'd be much farther apart. At airports with parallel runways, both are used by the planes are staggered in time so they don't end up side by side.
You wouldn't feel turbulence from a plane below you. There might have been some turbulence for him from your plane's wingtip vortices descending if they passed behind your plane's wings.

500 feet is about 150 meters, or half the minimum mentioned by Burhan Khalid. Since this is presumably about commercial flight (based on OP's mention of being aboard a KLM flight), it's likely a fairly safe bet that OP's flight was in controlled airspace at the time; can you specify where in controlled airspace a vertical separation of ~500 feet would be allowed, ideally with reference to Spanish or EASA regulations?

I cannot.  I was thinking VFR traffic flying below IFR traffic, VFR at east/west thousands + 500ft, IFR at east/west thousands.


text:
Why are the stabilised approach criteria different for an instrument approach and a visual approach?
My question mainly pertains to the simple altitude difference. Why is the stabilised call given at 1000ft for an instrument approach and 500ft for a visual approach?

There's no legal definition of "stabilised approach criteria", it's completely up to the air carriers

All instrument approaches are not alike. The Flight Safety Foundation Approach-and-Landing Accident Reduction Tool Kit, Section 5.1 — Approach Hazards Overview points out

Fifty-three percent of the accidents and incidents occurred during nonprecision instrument approaches or visual approaches (42 percent of the visual approaches were conducted where an instrument landing system [ILS] approach was available); …
Fifty-nine percent of the accidents and incidents occurred in instrument meteorological conditions (IMC); …

For a precision ILS approach, the ALAR recommends additional criteria in that the approach must be flown within one dot of the glideslope and localizer.
The thousand-foot gate is clearly driven by the worst case of a circling approach where the aircraft is not aligned with the runway, must transition off instruments back to visual flying, make the appropriate maneuvers, and land safely. Those all take time, so we should expect the recommendation to be at least as high as the visual approach.
In Section 7.1 — Stabilized Approach, we read

In addition, a stabilized approach provides

More time and attention for monitoring ATC communications, weather conditions and system operation;
More time for monitoring and backup by the PNF;
Defined flight-parameter-deviation limits and minimum stabilization heights to support the decision to land or to go around; and
Landing performance consistent with published performance.

So if the 1000ft gate if for the worst case scenario being a circling approach. What's with the 500 ft gate for the visual approach? As here we are in visual contact with the runway the whole time. Is that why it's lower?

How is 1000' gate about circling? Circling minima are often below 1000' and the circling often (especially in the most common case of flying downwind ILS and landing on that runway in opposite direction) includes level segment.


text:
What lights are used on top of a building or structure near an airport?
What type of light (strobe, beacon, color) should be displayed on top of a building or structure near an airport ?

For what country?

See also (for the US): Are red obstacle lights near an airport required to be lit during the day?

Country this question relates to is the Philippines.

I should also add that the building is only 23 m above ground. Located about 2km from the airport but not in it's flight path.

The general guidelines are:

4.3 Lighting Systems. Obstruction lighting may be displayed on structures as follows:

Aviation Red Obstruction Lights. Use flashing lights and/or steady-burning lights during nighttime. Tower structures are typically
  marked with flashing red lights. Buildings and smaller obstructions
  located near airports should be marked with steady-burning red lights.
  (See Chapter 5).
Medium-Intensity Flashing White Obstruction Lights. Medium-intensity flashing white obstruction lights may be used during
  daytime and twilight with automatically selected reduced intensity for
  nighttime operation. When this system is used on structures 700 feet
  (213 m) AGL or less, other methods of marking and lighting the
  structure may be omitted. Aviation orange and white paint is always
  required for daytime marking on structures exceeding 700 feet (213 m)
  AGL. This system is not normally recommended on structures 200 feet
  (61 m) AGL or less.
High-Intensity Flashing White Obstruction Lights. High-intensity flashing white obstruction lights may be used during daytime with
  automatically selected reduced intensities for twilight and nighttime
  operations. When this system is used, other methods of marking and
  lighting the structure may be omitted. This system should not be used
  on structures 700 feet (213 m) AGL or less, unless an FAA aeronautical
  study shows otherwise.
  Note: All flashing lights on a structure
  should flash simultaneously except for catenary support structures,
  which have a distinct flashing sequence between the levels of lights
  (see paragraph 4.4).
Dual Lighting. This system consists of red lights for nighttime and high- or medium-intensity flashing white obstruction lights for
  daytime and twilight. When a dual lighting system incorporates
  medium-intensity flashing white lights on structures 700 feet (213 m)
  AGL or less or high-intensity flashing white lights on structures
  greater than 700 feet (213 m) AGL, other methods of marking the
  structure may be omitted.

Specific details are spelled out in AC 70/7460-1L CHG1 Obstruction Marking and Lighting.


text:
Best study strategy for instrument checkride?
My instrument check ride is fast approaching, and I want to come up with a comprehensive study strategy to prepare. I feel a bit overwhelmed with the amount of information I feel I should memorize and understand. Other than flash cards, what other concrete strategies would you all recommend? Perhaps reading through and taking notes on the AIM, Instrument Flying Handbook, ect..?

Best way to master a topic is to teach it to someone else. If you know an instrument student who is just starting out, offer to coach them. Organizing the information for presentation and presenting it burns it in your brain better than anything.
Next best is to write about it. Write a series of short articles to yourself that outline the critical facts you have to have memorized.  It's basically note-taking, but a little more in depth. The mental process of sifting and organizing the info burns it in pretty good.
Critical procedures you have to recall from memory; repetition, repetition, repetition. Drill drill drill, then drill some more. Drill it until you can have someone distract you by poking you and yelling at you, as you recite memory items and procedures, unaffected by the poking and yelling. When you can do that, it's burned in well enough to come to you automatically when you're under stress during the check ride.
And don't forget to use MS Flight Simulator on your computer to practice. You have the ability to fly hundreds of approaches, holds, missed approaches, engine failure drills. Use it. Examiners are blown away by someone whose hands fly around effortlessly doing A/B/C/D while they are able to think ahead about what do to next. You achieve that through repetition and drill.

Yeah, flight sims can help here. Nowdays, many of them do offer real life nav aids tuning, cross wind, poor visibility with realistic instrument and plane behavior. You can actually fly your exam airfield in the sim. It can be time consuming though.

When I was flying CRJs, years ago, it was quite infrequent, and I actually used a CRJ add on for FSX to practice profiles, or to familiarize myself with a new destination. Even at that basic level, the ability to repeat things is a powerful tool. Recurrent check rides involved a non precision circling approach usually followed by a go around with an engine fire at just the right time during the climb out It was pretty intense doing it in a jet. But I'd done it hundreds of times at home, so it came easy.


text:
Why aren't ducted rotors used in gas turbines?
I am wondering why (for what I know) no gas turbine employs ducted enclosures for blade arrays on rotor stages.
I tried to search the internet for resources but I couldn't find anything related (so I'm not sure if the keywords I used were correct).
Anyway, I thought that a number of reasons would seem to justify such a solution:

Improved centrifugal resistance, especially if some sort of bearing system (hydraulic/electromagnetic maybe) is included around the duct
Higher blades bending stiffness, and thus reduced blade vibration
Better tip leakage retention

The only downside I can think of involves manufacturing complexity, but it doesn't look like an unsolvable problem to me.
So my question is: if these considerations hold, why are such kind of rotors not a thing?
EDIT
From comments and answers I understood my explanation was unclear.
What I meant with the term "ducted rotor" was for the rotor blades to be enclosed, on the tip side, by a cylindrical ring solid to the blades themselves, thus spinning together with them and constituting a physical constraint among them.

Thanks! Very interesting

I don't understand the question.  Aren't all turbine engines 100% contained within a duct?  Without ducting all uncontained air just spills out the side and the engine wouldn't even work...

Do you mean that the blade tips are mechanically attached to a duct that rotates with them?

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

If I understand your edit, the technical term for what you are looking for is called a "shrouded blade" or maybe a "tip shroud".  They are definitely used.  Google images will show you many pictures of them.  For example the picture below (taken from this article).
They can be used on any type of turbomachinery, but I've most often seen them used on lower speed turbines.  For high speed turbines, the centrifugal load of the shroud weight causes so much stress on the blades that it far outweighs the benefits of the shroud.  Two of the main benefits are exactly as you said: vibration and tip leakage reduction.

Why aren't ducted rotors used in gas turbines?

They are. There are actually two ducts forming an annular channel, as blades and vanes do not extend down to the rotating shaft. As air is more and more compressed, it takes less space, hence the channel area decrease continuously along the path.
These specific points:

I thought that a number of reasons would seem to justify such a solution:

Improved centrifugal resistance, especially if some sort of bearing system (hydraulic/electromagnetic maybe) is included around the duct
Higher blades bending stiffness, and thus reduced blade vibration
Better tip leakage retention

are linked to the use of shrouded blades. An answer already exists: Why do turbine rotors have an outer shroud but compressors don't?.
I'm answering only about how ducting is made, from an air-tightness standpoint.

A gas turbine engine includes a compressor to feed the engine in air, a combustor to burn fuel with air, and a turbine to spin the compressor.
Compressor and turbine are made of successive stages, each stage having fixed vanes (stator assembly) and rotating blades (rotor assembly). Vanes in a compressor stage follow blades and are divergent, in order to convert the excess of velocity created by the blades into static pressure. This is the opposite in a turbine stage, they come first to convert pressure into velocity to rotate the blades behind.
Compressor and turbine are ducted, though the ducts are made of several sections. The ducting of the turbine is more complex.
Compressor
Stators and rotors are assembled in a way which creates two ducts:

A rotating inner duct holds the rotor blades. It has tracks on which the inner tips of the stator vanes slide. These tracks are usually labyrinth seals to prevent air from bypassing the vanes.

A fixed outer duct holds the stator vanes. It has tracks on which the outer tips fo the rotor blades slide. This time the tracks are flat, made of abradable material in order to fit the length of the blades. The first stators have vanes which can rotate along their radial axis in order to adjust the angle of attack and keep the engine in optimal working conditions.

This is the high-pressure compressor from a CMF56-7B (Boeing 737 NG):

Source: Airbus engine training manual.
You can see yellow-higlighed the two walls of the annular duct. Rotating blades are marked with green dots. This duct is air-tight enough for the compressor function. However a lot of air leaves it without going to the combustor: Bleed air tapped in the cavity you see on the right, air used for engine cooling, etc.
The high-pressure turbine spins the inner drum, and the outer casing is fixed to the fan frame which is a mounting point of the engine, fixed to the wing.
Turbine
Turbines are working at high temperature, because a combustor generating a higher temperature gas increases the engine efficiency. The consequence is turbine blades and vanes work near their limits in term of temperature, as well as the outer wall of the ducting.
The ducting is therefore designed to help cool the turbine, leading to a more complex assembly, with holes for cooling air. It must also adapt to a higher dilatation. The shroud at this level is composed of individual segments which can move (HPTCC below), rather than simply using an abradable material.
The high-pressure turbine for the same engine:


text:
Energy Maneuverability Theory Applied to WW1 Fighters
I am trying to test the Fokker D.VII, Spad S.XIII, Sopwith Camel, Nieuport 28, and the Se5a using the model in this paper:
https://apps.dtic.mil/sti/pdfs/ADA066034.pdf
It's called Combat Performance Advantage and is derived from EM theory.  My question:  How are they reaching these Ps values, and how can I do the same using the data I have?  They have an example calculation on page 14/15, and before that provide some details on the model.
I have the aircraft weight, fuel weight, zero lift drag coefficient, wingspan (reference area), maximum lift coefficient, aspect ratio, maximum instantaneous and sustained turn rates (at 4km altitude), and a few other things.  I was able to estimate the Oswald efficiency factor and a couple of other metrics.  I'm still not clear on how to combine these to get the power lost during a turn in the attached paper, although I was able to calculate t Alpha and t Theta.
Thanks in advance for any help you can provide.

EM theory may have more to do with retaining speed and the ability to go vertical.  WW1 planes did not have the power to do much of that.  Instead, they flew tight turns as near to stall as possible to try to gain advantage.  They also were very draggy compared to more modern aircraft.

$P_s=\frac{(T-D)V}{W}$
Which is written for a jet aircraft (in terms of thrust).  If we write it for a prop...
$P_s=\frac{P_a-P_r}{W}$ where $P_a$ is power available and $P_r$ is power required.
Power available is the propeller efficiency times the available shaft power.
$P_a=\eta_p \, P_\mathrm{shaft}$
For WWI aircraft (fixed pitch props), this calculation is more complex than you might think to do right.  In particular, the difference in props may be the difference between two aircraft's capabilities at a certain point in the flight envelope.
$P_r=D \, V$
$D = C_D \, q \, S$
Here we'll assume a simple parabolic drag polar.  There really should at least also be a term that is linear with lift.  However if you don't have detailed drag polars for the aircraft, that won't matter.
$C_D = C_{D,0} + K \, {C_L}^2$
$C_L=\frac{L}{q\,S}$
And here is where turning flight comes in...
$L=n \, W \, \cos(\theta)$
Where $n$ is the load factor -- if the aircraft is pulling two gees, then $n=2$.
The $\cos(\theta)$ here is often ignored (particularly for relatively low performance aircraft).  It introduces two complications -- 1) the solution becomes iterative as $P_s$ depends on $\theta$ while it also determines $\theta$.  If you need, some quick iteration will sort this out.  2) it depends on pilot intent -- are you putting the excess power into climb, or into horizontal acceleration, or both.  You can even dive with positive $P_s$ to really pick up speed.
In particular, when most interested in maximum sustained turn rate, the definition of that point is $\theta=0$, so the problem is avoided.
So, to answer what I believe is your question...  The additional induced drag from pulling gees during a turn increases the power required and thereby decreases the Excess Power.
I believe this is what you mean by the "power lost during a turn".


text:
How do aircraft throttle levers allow the pilot to move the levers, as well as motors to move the levers for autothrottle?
Boeing and Airbus throttle levers have an autothrottle feature that allows the levers to move automatically, as well as the normal input from the pilot. How is the motor and mechanics designed to allow these two different control inputs?
I would guess that the motor used to control the levers is a stepper motor. However, when the pilot moves the levers he will feel a resistance force from the motor trying to put the rotor back to its original position.
How does the throttle lever have two different input methods?
I would guess that a hall effect sensor is used to read the movements from the pilot to prevent the autothrottle motor moving the lever back to the original position.
A youtube video of the inside mechanics would be beneficial, however, I cannot find one.

Motorized faders in audio mixing desks just use a slipping clutch, I don't know that aircraft controls do the same but it's quite likely.

Airbus actually doesn't use autothrottles anymore (since the A320). They use autothrust, where the thrust levers in the cockpit don't move when the computer commands different thrust (they typically stay in the CLB detent).

Can you explain why there should be any difficulty and what research you did?

@user_1818839 I think that's the approach in some "full-time MF" SLR camera lenses too.

@SolarMike presumably depends whether the thing is constructed according to the Boeing or Airbus mindset - whether the computers have to actually move the flight controls to do what they want (computers ==> control levers ==> more computers ==> plane), or whether the computer does what it wants and the flight controls are just inputs (control levers ==> computers ==> plane)

The exact details for the autothrottle system obviously depend on the aircraft. I will focus on the Boeing 777 as an example here.
The B777 FCOM (Flight Crew Operating Manual) describes the thrust lever operation like this:

Autothrottle Thrust Lever Operation
The autothrottle system moves either or both thrust levers to provide
speed or thrust control, depending on the active mode.
Thrust levers can be manually positioned without disconnecting the
autothrottle. After manual positioning, the autothrottle system
repositions thrust levers to comply with the active mode. The
autothrottle system does not reposition thrust levers while in HOLD
mode.

(Boeing 777 FCOMv2 4.20.9 - Automatic Flight - System Description)
The thrust lever block on the 777 looks like this:

[...] The servo motor/gearbox installation is located below
the throttle levers with direct mechanical linkage to the
levers via over-ride slip clutches. [...]

(D Wilkinson, Data Bus Technology Applications—Boeing 777 Autothrottle Servo Motor)
These over-ride slip clutches allow the pilot to move the thrust levers against autothrottle input. The use of such slip clutches is quite common, also for the autopilot (see e.g. this answer).
The internal components of the autothrottle servor motor (ASM) are shown in this picture:

The unit consists of a high efficiency brushless d.c.
motor, single-stage 9 to 1 ratio reduction gearbox and
output drive spline, together with the ‘smart’ control
electronics, contained in a support housing providing
the required ARINC 558 mechanical interface plus electrical interface via a pigtail cable and connector. [...]
The high efficiency brushless d.c. motor has an 18
pole stator with delta three-phase windings and a 6 pole
rotor using high energy samarium cobalt rare-earth
magnets. Three bi-polar latching Hall Effect sensors
detect shaft rotation for commutation and tacho rate
information.

(D Wilkinson, Data Bus Technology Applications—Boeing 777 Autothrottle Servo Motor)

I've flown the corporate version of the CRJ with an STC'd autothrottle system with add-on always-engaged servos driving the thrust levers, and what I didn't like was the friction control components were removed and the friction setting became the slip clutch force of the AT servos, and you couldn't change it. and it was a lot higher than I liked, especially when flying approaches.